<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    var name = "window";

    var person = {
        name: "person",
        sayName: function () {
            console.log(this.name);
        }
    };

    function sayName() {
        // 最外层的this = window
        var sss = person.sayName;
        sss(); // window
        person.sayName(); // person
        (person.sayName)(); // window  这里错了 实际应该是  person  这个括号没有任何意义,并没有改变执行顺序,和 person.sayName();完全一致
        (b = person.sayName)(); // window
    }

    sayName();


</script>

</body>
</html>